Mobile roof drill



Oct. 29, 1957 J. R. FLETCHER ETAL 2,811,335

MOBILE ROOF DRILL Filed Nov. 19. 1952 5 Sheets-Sheet 1 INVENTORS. JamesFaber! F/e faker Wd/iam Fara/e7! Tlezcke: Ida/4.5 Z T E Oct 1957 J. R.FLETCHER ETAL' 2,811,335

MOBILE ROOF DRILL Filed Nov. 19, 1952 5 Sheets-Sheet 2 6] 63 o L W" 45:91 IO 53 41 I07 w I ll INVENTORS. James Faberf F/e tC/Iez 'lliamTara/ell Fletcher b Q HZ Z HE Oct. 29, 1957 J. R. FLETCHER ETAL MOBILEROOF DRILL 5 Sheets-Sheet 5 Filed NOV. 19, 1952 a 5 M H M U m H w m Oct.29, 1957 J, FLETCHER E 2,811,335

MOBILE ROOF DRILL Filed Nov. 19, 1952 5 Sheets-Sheet 4 INVENTORS. limesEbert Fletcher 1T. 3 mm Fame/l Wezc/zer Oct. 29, 1957 Filed Nov. 19,1952 MOBILE ROOF DRILL 5 Sheets-Sheet 5 no I09 Iig-El 97 94 L,INVENTORS.

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& H am Fara/e]! Fletcher E Z 2 H5 United States Patent Office 2,811,335Patented Oct. 29, 1957 MOBILE ROOF DRILL James Robert Fletcher andWilliam F. Fletcher, Huntington, W. Va., assignors to J. H. Fletcher &Co., Chicago, 11]., a corporation of Illinois Application November 19,1952, Serial No. 321,344

10 Claims. (Cl. 255-51) This invention relates to improvements in mobileroof drills and more particularly relates to such a drill having a dropmast taking the drilling reaction on the ground.

A principal object of our invention is to provide a mobile roof drillfor drilling holes directly in the mine roof to receive roof bolts, in amore expeditious manner than formerly.

Another object of our invention is to provide a novel and improved formof mobile roof drill for drilling vertical holes in a mine roofparticularly adapted for operation in thin seams of coal.

A further object of our invention is to provide a novel and improvedform of roof drill having a drilling carriage supported for verticalmovement against a drop mast reacting against the mine floor duringvertical feeding movement of the carriage for drilling in a mine roof.

A still further object of our invention is to provide a novel andimproved form of self-propelled drilling apparatus for drilling holesupwardly in the mine roof, arranged with a view toward providing a firmsupport for the drilling mechanism during the entire drilling operationand increasing the travel of the drill carriage and making itunnecessary to change drill during the normal operation of drilling inthe roof, to receive a roof-supporting bolt.

A further object of the invention is to provide stability for the mast,so that after the hole is drilled and the bolt inserted, the drill chuckmay be maintained in alignment with the bolt head and be used to tightenthe bolt.

A still further object of our invention is to provide a mobile roofdrill, particularly adapted to drill holes for roof bolts in minesunderground wherein a drop mast forms a support for the drill and drillcarriage and the mast is so arranged as to take the drilling reactionagainst the ground and to accommodate the drill carriage to first travelthe height of the collapsed mast and then to travel a further distanceequal to the length of extensible movement of the mast.

A further and more detailed object of our invention is to provide aself-propelled roof drill wherein a mast assembly is guided on a mobileframe for vertical movement with respect thereto and has a drill guidedfor vertical movement therealong and in which a cylinder and piston unitsets the mast assembly on the floor and an additional two stage cylinderand piston unit moves the drill carriage along the mast assembly duringone stage of extensible movement thereof and then moves the assembly andcarriage a further distance during a second stage of extensible movementthereof.

These and other objects of our invention will appear from time to timeas the following specification proceeds and with reference to theaccompanying drawings wherein:

Figure l is a top plan view of a mobile roof drill constructed inaccordance with our invention;

Figure 2 is a view in side elevation of the drill shown in Figure 1Figure 3 is a front end view of the drill shown in Figures 1 and 2;

Figure 4 is a fragmentary view in side elevation of the forward endportion of the drill frame and mast, showing the drop mast and drillcarriage in engagement with the ground;

Figure 5 is a view somewhat similar to Figure 4, but showing the dropmast and drill carriage in a fully extended position;

Figure 6 is a front end View of the drop mast and drill carriage showingthe drop mast and carriage in the extended position shown in Figure 5;

Figure 7 is an enlarged fragmentary plan view of the front end of thedrilling apparatus showing certain details of the mast and supporttherefor, not shown in Figure 1;

Figure 8 is a diagrammatic view showing the fluid diagram for operatingthe drill and extending and tilting the drop mast and drill carriage;and

Figure 9 is a transverse sectional view taken through the two stagefluid pressure cylinder and piston for feeding the drill carriage alongthe drop mast and then extending the mast and carriage therewith.

In the embodiment of our invention illustrated in the drawings a truck10 is shown as including a main frame 11 mounted on front tractionwheels 12, 12 and a rear steering wheel 13.

The frame 11 is shown as having an operators compartment 14 at one sidethereof having a steering wheel 15 therein operatively connected withthe rear steering wheel 13 for turning the same and steering the vehiclethrough a chain and sprocket drive 16.

A motor 17 is also shown as being mounted on the main frame 11 and ashaving driving connection with a pump 19 through a flexible coupling 2%.The motor 17 may be controlled by a controller 21 on the opposite sideof the frame from the operators compartment 14, which may be operatedfrom the operators compartment in a suitable manner. The motor 17 mayalso be connected with the front traction wheels 12, 12 for driving thesame in any well known manner, and not herein shown or described sinceit forms no part of our present invention.

At the front end of the main frame 11 and extending transversely thereofbetween the wheels 12, 12 is a vertical support plate 22 for a drop mast23. The drop mast 23 is herein shown as comprising a channelled guide 24mounted on and extending forwardly from a tiltable plate 25, shown asbeing pivotally mounted on the plate 22 adjacent the lower end thereofon a pivot pin 27 extending longitudinally of the frame 11. The plate 25is shown as having an arcuate slot 26 adjacent its upper end withinwhich extends a headed pin or bolt 30, mounted on and extendingoutwardly from the plate 25. A collar may encircle said pin and beinterposed between said plates and a nut may be threaded on the innerend of the pin 30, to hold the outer plate 25 in parallel relation withrespect to the plate 22. The outer plate 25 is shown as being tiltableabout the axis of the pin 27 by means of a fluid pressure cylinder 31having a piston (not shown) movable therein and a piston rod 33extensible therefrom. The cylinder 31 is shown as having an ear 34projecting outwardly from its head end, which is pivotally connected tothe left-hand upper corner of the support plate 22 on a pivot pin 35.The piston rod 33 is shown as being connected with the plate 25 forpivoting the same about the axis of the shaft 27 on a pivot pin 36secured to and extending inwardly from the plate 25. Fluid underpressure may be admitted to and released from the head and piston rodends of the cylinder 31, and may be held therein to hold the plate 25 inthe desired position of adjustment under the control of a valve 37 in avalve bank 38. Pressure lines 39 and 40 leading from the valve 37 areshown as being connected to the head and piston rod ends of the cylinder31, respectively (see Fig. 8) to sup- J ply and release fluid therefromand to hold fluid under pressure therein under control of the valve 37,in an obvious manner.

The channelled guide 24 on the plate 25 is shown in Figure 7 ascomprising two spaced, inwardly facing angles 41, 41 extendingvertically along said plate and suitably secured thereto as by welding.Spaced blocks 42, 42, extend along the plate 25 and a leg of each angleto form the inner guide of the channelled guide. Said blocks terminateshort of the arcuate slot 26 and space the drop mast outwardly from thehead of the pin 30.

Slidably guided within the channelled guide 24 is the drop mast 23. Saiddrop mast is shown as having a drill carriage 44 slidably guided thereinfor vertical movement therealong. The drop mast 23, as herein shown,comprises two facing channels 45, 4S guided for vertical movement alongthe channelled guide 24. The drop mast 23 also includes two facingchannels 47, 47 slidably guided within the channels 45, 45 forextensible movement therefrom. The channels 45, 45 are shown as beingconnected together at their lower ends by a base plate 49 engageablewith the ground and reacting thereagainst during the drilling operation.

The base plate 49 of the drop mast 23 is herein shown as being movedinto and out of engagement with the ground by means of a fluid pressurecylinder 50 having a piston (not shown) movable therein and a piston rod51 extensible therefrom. The cylinder 50 is shown as having a lug 53extending from its head end, pivotally connected to the left-hand angle41 adjacent the upper end thereof on a pivot pin 54. The free end of thepiston rod 51 is shown as being pivotally connected to the lower end ofthe left-hand channel 45 of the drop mast 23 on a pivot pin 55. Fluidunder pressure may be admitted to the head and piston rod ends of thecylinder 58 to raise and lower the channels 45, 45 and base plate 49 ofthe drop mast 23, and engage the base plate 49 with the ground, by meansof a valve 56 in the valve bank 38 and pressure lines 57 and 58 leadingfrom said valve to head and piston rod ends of the cylinder 50 (see Fig.8).

The channels 47, 47 slidably guided within the channels 45, 45, areshown as being connected together adjacent their upper ends by a tieplate 61. A drill guide 63 is shown as extending forwardly therefrom andforming a guide for a drill 65, carried at its lowered end in a chuck 66in the drill carriage 44. The drill guide 63 may be of any well knownform and is not herein shown or described in detail since it forms nopart of our present invention.

Slidably supported and guided within the channels 47,47 is the drillcarriage .4. Said drill carriage is shown as comprising two framemembers 67, 67 each of which has spaced rollers 69, 69 rotatably mountedthereon and fitting within the channels 47, 47 and riding along theflanges thereof. The frame members 67, 67 are shown as being connectedtogether by a vertical plate 70 spaced forwardly of the channels 47, 47.Attached to the plate 79 and extending forwardly therefrom is a baseplate 71 having a fluid motor 73 mounted thereon and also having ahousing 74 mounted thereon and forming a housing and bearing support forthe chuck 66 and the drive mechanism therefor.

The fluid motor 73 is shown in Figure 7 as driving the chuck 66 througha chain and sprocket drive 75 and spur reduction gearing 76 driventhereby. A clutch (not shown) operated by a hand lever 78 may beprovided to selectively connect the chain and sprocket drive 75 with thegearing 76. The fluid motor 73 may be operated in reverse directionsunder the control of a valve 77, which may be mounted on a support plate79 extending outwardly from the right channel 45 adjacent the right-handend thereof (see Figures and 8). Fluid under pressure may be supplied tosaid valve from the pump 19 through a pressure line 80 connected fromsaid pump to said valve, the return from said valve being through re- 4I turn lines 81 and 82 leading to a tank (not shown). The valve 77 isconnected with opposite sides of the drill motor 73 to supply fluidunder pressure to either end thereof by means of pressure lines 83 and84, it being understood that when fluid under pressure is supplied toone end of the drill motor 73 through one pressure line that it isreleased from the opposite end of said drill motor through the otherpressure line.

The pump 19 is shown in Figure 8 as being a dual pump driven by anelectric motor 116. One section 117 of the pump 19 receives fluid fromfluid storage tank 119 and serves to supply fluid to the pressure lineand the drill motor 73. Another section 120 of the pump 19 is connectedwith a fluid storage tank 121 and delivers fluid to the valve bank 38through a pressure line 122. A flow control valve 123 is connected insaid pressure line and also serves as a relief valve.

The means for feeding the drill carriage 44 along the channels 47, 47and then extending the channels 47, 47 from the channels 45, 45 is shownas comprising a two stage fluid pressure cylinder 85, which may bedouble acting, and has a piston rod 86 extending downwardly therefrominto engagement with a socket and fitting 87 on the base plate 49 (seeFigure 6).

As shown in Figure 9, the two stage cylinder has an outer casing orshell 89 having an inner casing or cylindrical shell 90 spaced inwardlytherefrom and sealed to the wall thereof and extensible therefrom.

The piston rod 86 in turn is shown as being hollow and as being slidablymovable within a cylinder 91. The cylinder 91 is secured at its innerend to a retainer 93 threaded within the outer shell 89. The retainer 93is shown as having a sealing member 94 threaded therein, having slidableengagement with the piston rod 86 and forming a seal and slidable guidetherefor. The end of the cylinder 91 opposite from the retainer 93 orend closure for the cylinder 89 is shown as being closed by an endclosure cap 95 threaded therein and sealed thereto. The cylinder 91 isshown as being connected at its upper end on the end closure cap 95 tothe tie plate 61 connecting the channels together at their upper endsand as having abutting engagement with the bottom of said tie plate. Apressure line 98 leading from a valve 96 shown as being in the samevalve bank as the valves 37 and 56, is connected with a port 97 leadingthrough the cylinder 89, and is also connected with the upper end of thecylinder 91 through a port 99 leading through the cap 95 to the interiorof said cylinder. When the valve 96 is in position to supply fluid underpressure to the ports 97 and 99, due to the increased surface areawithin the cylinder 89, fluid will first act on the inner cylinder 90and move said cylinder upwardly along the cylinder 89 for the length ofstroke thereof. Fluid under pressure also entering the interior of thecylinder 91 will then react against a piston 101 within said cylinderand on the upper end of the piston rod 89, bodily moving the cylinder 91and the cylinders 89 and 90 along the piston rod 86 as a unit. A port103 enters the cylinder 89 at a point spaced above the bottom thereofand is connected with the valve 96 through a pipe 104. The pipe 104 isalso connected with a port 105 at the lower end of the piston rod 86admitting fluid under pressure to the hollow interior of said pistonrod. When the valve 96 is in position to admit fluid under pressurethrough the pipe 104, fluid under pressure entering the port 103 willfirst move the cylinder 90 downwardly within the cylinder 89. Fluidentering the interior of the cylinder 91, through the port 105, willthen react against said piston in a direction to retract the cylinder 91along the piston rod 86 and retractably move the cylinder 89 therewith.

The connection between the cylinder and piston unit 85 and the drillcarriage 44 is shown as including two flexible devices, such as chains107, 107. The chains 107, 107 are shown as being secured to the outerend of the cylinder 89 at one of their ends on connectors 108, 108 andas extending upwardly therefrom over rollers 109, 109 rotatablyjournaled on a collar 110. The opposite ends of the chains 107, 107 aresuitably connected to the drill carriage 44 to effect movement of saiddrill carriage along the channels 47, 47 upon extension of the innercasing 90 from the outer casing 89. The collar 110 is shown asencircling the cylinder 90 and as resting on the upper end thereof.Since the pull of the chains 107 are always in a downward direction withrespect to the rollers 109, 109 and since said chains take the weight ofthe carriage 44, the collar 110 will be retained in engagement with theupper portion of the cylinder 90 by the weight of the drill carriage 44.A snap ring 111 which may be snapped within the collar 110 and engage arecessed portion 111a of the cylinder 90 is provided to retain thecollar 110 from upward lifting movement with respect to the cylinder 90.

Thus, when the reaction plate 49 is in engagement with the ground andthe valve 96 is in position to admit fluid under pressure to the ports97 and 99, the collar 110 and rollers 109, 109 will first move upwardlyrelative to the cylinder 89, moving the drill carriage 44 upwardlytherewith. When the cylinder 91 reaches the upper limit of its travel,as when a sealing ring collar 114 abuts a shouldered surface 115 on theinner periphery of the cylinder 89, fluid pressure entering the cylinder91 through the port 99 will act on the piston 101 and extend thecylinder 91 along the piston 86 for the limit of travel thereof, movingthe cylinders 90 and 89 and drill carriage 44 and drill 65 therewith.

Upon movement of the valve 96 into a position to admit fluid underpressure to the ports 103 and 105 the entire drill carriage will belowered, withdrawing the drill carriage and drill from the roof in anobvious manner.

It may be seen from the foregoing that we have provided a novel andimproved form of drill, particularly adapted to drill holes in a mineroof for roof bolts with expansion shields to hold the weaker rockstrata to the firmer rock, which is so arranged that the reaction todrilling is taken on the mine floor, permitting high pressures to beapplied against the rock roof when drilling, and thus enabling harderrock to be drilled faster than formerly, with a resultant increase inlife of the drill bit.

It may further be seen that the device of our invention is of a simpleform, utilizing a telescopic drop mast movable into engagement with theground and then feeding the drill upwardly in two stages, with aresultant increased length of drill travel, enabling the use of relatively long drills, and reducing the number of drill changes during adrilling operation.

It may still further be seen that as a result of the added drill travelobtained by lowering the mast and drill carriage into engagement withthe ground, the drill of our invention is particularly adapted for usein thin seams of coal, since the required depth of hole may be drilledwith longer drills and fewer drill changes than formerly.

It will be understood that modifications and variations may be effectedwithout departing from the scope of the novel concepts of the presentinvention.

We claim as our invention:

1. A mobile roof drill comprising a wheel mounted frame, guide means atone end of said frame having a vertical guideway extending therealong, afirst guide track guided in said guideway for vertical movementtherealong, a second guide track guided in said first guide track forvertical movement along said first guide track, said first guide trackhaving a bearing plate at the lower end thereof engageable With theground, a drill carriage having a vertical drill therein, means guidingsaid drill carriage for movement along said second guide track, fluidpressure means mounted on said bearing plate and extending upwardlytherefrom and having connection at its upper end with said second guidetrack for moving said second guide track vertically along said firstguide track, other fluid pressure means encircling said first mentionedfluid pressure means and having connection with said carriage and withsaid first fluid pressure means and being movable along said first fluidpressure means, for moving said carriage upwardly along said secondmentioned guide track, and a drill guide on the upper end of said secondguide track having guiding engagement with said drill.

2. A roof drill comprising a mobile frame, a stationary vertical guideat one end of said frame comprising a pair of facing verticallyextending guideways, a telescopic guide track guided for movement alongsaid guideways and having a bearing plate at the lower end thereofengageable with the ground, a fluid pressure cylinder and piston unithaving a piston rod mounted on said bearing plate and having a firstcylinder connected with said guide track for extensibly and retractiblymoving the same, a second fluid pressure cylinder and piston unitencircling said first cylinder, said second mentioned cylinder andpiston unit having a piston unit encircling said first cylinder andbeing movable therealong, a drill carriage guided for movement alongsaid guide track, and an operative connection between said fluidpressure cylinder and piston unit and said carriage for effectingmovement of said carriage along said guide track upon movement of saidpiston unit with respect to said cylinder, and for effecting movement ofsaid carriage with said telescopic guide track upon extension thereof byextension of said first cylinder along said piston rod.

3. A self-propelled roof drill comprising a mobile frame, a stationaryguide at one end of said frame comprising a support plate pivoted onsaid frame for movement about a horizontal axis and having a pair offacing guideways mounted thereon, an outer guide track guided in saidguideways for movement therealong, a bearing plate carried by said outerguide track for engagement with the ground, an inner guide track guidedfor telescopic movement along said outer guide track, a drill carriageguided in said inner guide track for movement therealong and formovement therewith, a fluid pressure cylinder and piston unit comprisinga first cylinder having connection with the inner of said guide tracksat its upper end and having a piston rod extensible therefrom mounted onand extending upwardly from said bearing plate, a second cylinder andpiston unit encircling said first cylinder and piston unit andcomprising an outer cylinder encircling said first mentioned cylinderand secured thereto, and an intermediate piston unit extensible withrespect to said outer cylinder and movable along said first cylinder,and a flexible feeding member connecting said intermediate piston unitwith said carriage for feeding said carriage along the inner of saidguide tracks upon extensible movement of said intermediate piston unitwith respect to said outer cylinder, and holding said carriage to eifectmovement of said carriage with the inner of said guide tracks uponextensible movement of said first cylinder along said piston rod.

4. In a drilling apparatus of the class described, a wheel mountedframe, a channelled guide at one end of said frame, a channelled guidetrack guided in said channelled guide for vertical movement therealongand having a bearing plate at one end thereof engageable with theground, a second channelled guide track guided in said first channelledguide track for extensible movement with respect thereto, a drillcarriage guided for movement along said second channelled guide track, atwo stage cylinder and piston unit mounted on and extending upwardlyfrom said bearing plate and operatively connected with said secondchannelled guide for extending said second channelled guide with respectto said first channelled guide, said two stage cylinder and piston unitincluding a piston rod engaging said bearing plate, a cylinder movabletherealong and connected With said second channelled guide, an outercylinder connected with said first mentioned cylinder and encircling thesame and extending th'erealong for a part of the length thereof, anintermediate piston unit movable along said first mentioned cylinder andextensible from said outer cylinder, means limiting extensible movementof said intermediate piston unit with respect to said outer cylinder, aflexible feeding member connected with said intermediate piston unit andhaving connection with said carriage for vertically moving said carriagealong said guide track upon extensible movement of said intermediatepiston unit with respect to said outer cylinder, and said outer cylinderand intermediate piston units being extensible together along saidpiston rod at the limit of travel of said intermediate piston unit, foreffecting movement of said carriage with said second guide track uponextensible movement thereof. i

5. In a drilling apparatus of the class described, a wheel mountedframe, a guide on said frame having a guideway extending verticallytherealong, a guide track guided in said guideway for vertical movementtherealong and having a bearing plate at one end thereof for engagementwith the ground, a second guide track guided for movement along saidfirst guide track, a drill carriage having a vertical upwardly facingpower driven drill guided for movement along said second guide track, atwo stage hydraulic cylinder and piston unit including a cylinde'rhaving'connection with said second guide track, a piston rod extensiblefrom said cylinder and mounted on and extending upwardly from saidbearing plate, an outer cylinder extending along said first mentionedcylinder for a portion of the length thereof and connected with saidfirst mentioned cylinder for movement therewith, an intermediate pistonunit within said outer cylinder and movable along said outer cylinderand extensible therefrom, a stop limiting movement of said intermediatepiston unit along said outer cylinder said intermediate piston unithaving a direction changing roller mounted thereon for movementtherewith and spaced vertically from said outer cylinder, and a flexiblefeeding member connected at one end with said outer cylinder and trainedabout said direction changing roller and connected at its other end withsaid carriage, for moving said carriage along said second guide trackupon extensible movement of said intermediate piston unit from saidouter piston unit, and then effecting movement of said carriage withsaid second guide track upon engagement of said intermediate piston unitwith said stop and movement of said intermediate piston unit and saidouter cylinder with respect to said piston rod upon extensible movementof said first mentioned cylinder along said piston rod.

6. In a drilling apparatus particularly adapted to drill holes in a mineroof to set roof bolts therein, a frame, an upright guide track, agenerally vertically extending guide means on said frame guiding saidtrack for vertical movement with respect to said frame, a drill carriageguided for movement along said track and having a rotatably driven drillchuck, fluid pressure operated means mounted on said guide means andhaving operative connection with said guide tracks for moving said guidetrack relative to said frame to a position adjacent the ground and forholding said guide track in engagement with the ground to take thereaction of drilling on the ground, and other fluid pressure meansconnected with said carriage for moving said carriage vertically alongsaid guide track to effect vertical feeding movement thereof.

7. In a drilling apparatus of the class described, a Wheel mountedframe, a channelled guide at one end of said frame adapted to extend ina vertical direction, a telescopic guide track guided in said channelledguide for vertical movement therealong, said telescopic guide trackhaving inner and outer guides having a bearing plate at one end of theouter of said guides and adapted to engage the ground, a hydrauliccylinder and piston unit connected with the outer of said guides andoperable to engage said bearing plate with the ground and lift the sameabove the ground, a drill carriage guided for movement along the innerof said guides of said telescopic guide track, a two-stage hydrauliccylinder and piston unit supported on said bearing plate at one end andconnected with the innertof said guides of said telescopic guide trackfor extending the same upon the admission of fluid under pressurethereto, said two-stage hydraulic cylinder and piston unit: including anouter cylinder, an intermediate piston unit extensibly movable withrespect to said outer cylinder,.means limiting extensible movement ofsaid intermediate piston unit with respect to said outer cylinder, andan inner cylinder and piston unit within said intermediate piston unit,a flexible feeding member operated by said intermediate piston unit andhaving engaging connection therewith and having fixed connection withsaid carriage for vertically moving said carriage along said guide trackupon extensible movement of said intermediate piston unit, and saidouter cylinder and said intermediate piston unit being movable togetheralong said inner'cylinder and pistonunit upon engagement of saidintermediate piston unit with said means limiting extensible movement ofsaid intermediate piston unit with respect to said outer cylinder, forextending said guide track and carriage therewith.

8. In a drilling apparatus of the class described, a wheel mountedframe, a channelled guide at one end of said frame and extending in agenerally vertical direction, a telescopic guide track guided in saidchannelled guide for vertical movement therealong, said telescopic guidetrack having inner and outer guides, a bearing plate connected with oneend of the outer of said guides for engagement with the ground, ahydraulic cylinder and piston unit connected between said channelledguide and the outer of said guides for engaging said bearing plate withthe ground and lifting said bearing plate above the ground, a drillcarriage guided for movement along the inner of said guides of saidtelescopic guide track, a two-stagehydraulic cylinder and piston unitmounted on said bearing plate at one end and connected with the inner ofsaid guides of said telescopic guide track at its opposite end, saidtwostage hydraulic cylinder and piston unit including an outer cylinder,an intermediate piston unit extensibly movable relative to said outercylinder, mean'siimiting the extensible movement of said intermediatepiston unit with respect to said outer cylinder, and an inner cylinderand piston unit Within said intermediate piston unit, said intermediatepiston unit having a-direction changing roller mounted thereon invertically spaced relation with respect to said outer cylinder, and aflexible'feeding member connected at one end with said outer cylinderand trained about said direction changing roller and connected at itsother end with said carriage, for moving said carriage along saidtelescopic guide track upon the admission of fluid under pressure tosaid outer cylinder to extend said intermediate piston unit along saidouter cylinder and moving said carriage with said guide track uponengagement of said intermediate piston unit with said means limitingmovement of said intermediate piston unit with respect to said outercylinder effected by movement of said intermediate piston unit and saidouter cylinder along said inner cylinder and piston unit.

1 9 A self-propelled roof drill comprising a mobile frame, a stationaryguide at one end of said frame comprising a support plate pivoted onsaid frame for movement about a horizontal axis and having a pair offacing guide members mounted thereon forming a guideway positionable toextend in a vertical direction, a telescopic guidetrack having an outerguide track guided for move ment along said guideway and an inner guidetrack guidediin said outer guide'track for extensible movement withrespect thereto, a bearing plate connected to one, end of said outerguide track and adapted to engage the ground, a fluid pressure cylinderand piston unit' connected between said frame and support plate fortiltingsaid support plate and guideway about a horizontal axis, a secondfluid pressure cylinder and piston unit connected between said supportplate and the outer of said guide tracks for moving said guide track ina direction to engage said bearing plate with the ground, a drillcarriage guided in the inner of said guide tracks for movementtherealong, a two-stage cylinder and piston unit mounted on said bearingplate and having connection with the inner of said guide tracks forextensibly moving the same with respect to the outer of said guidetracks, said two-stage cylinder and piston unit including an outercylinder, an intermediate piston unit mounted for extensible movementwith respect to said outer cylinder, means limiting extensible movementof said intermediate piston unit with respect to said outer cylinder,and an inner cylinder within said intermediate piston unit and having apiston rod extensible therefrom and carried on said bearing plate, aflexible feeding member fixedly connected with said outer cylinder atone end and With said carriage at its opposite end, a direction changingmember on said intermediate piston unit spaced vertically from saidouter cylinder and having said flexible feeding member trainedthereabout, for moving said carriage along said inner guide track uponextensible movement of said intermediate piston unit into an engagementwith said means limiting extensible movement thereof, said outercylinder and intermediate piston unit then moving with said innercylinder along said piston rod and moving said inner guide track andcarriage as a unit.

10. A roof drill comprising a mobile frame, a telescopic guide track atone end of said frame and including facing outer and inner guide tracksnormally extending in a vertical direction, one of which istelescopically movable with respect to the other, guide means on saidframe having a vertically extending guideway extending therealong havingguiding engagement with the outer of said guide tracks and guiding saidguide tracks for vertical movement with respect to said frame, a bearingplate at one end of one of said guide tracks engageable with the ground,a drill carriage having a drill chuck and a motor for rotatably drivingsaid chuck, means guiding said carriage for movement along the inner ofsaid guide tracks, fluid pressure means mounted on said guideway andhaving operative connection with the outer of said guide tracks formoving said bearing plate into engagement with the ground, other fluidpressure means supported on said bearing plate and having connectionWith the inner of said guide tracks for raising and lowering said guidetrack along the outer of said guide tracks, and means connecting saidother fluid pressure means with said drill carriage for moving saiddrill carriage upwardly along the inner of said guide tracks.

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